[Chromecast] Add support for different playback rates to ALSA backend

chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chromecast/media/cma/backend/alsa/stream_mixer_alsa_input_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/bind.h"
@@ skipping 65 matching lines @@
       state_(kStateUninitialized),
       slew_volume_(kMaxSlewTimeUpMs, kMaxSlewTimeDownMs),
       queued_frames_(0),
       queued_frames_including_resampler_(0),
       current_buffer_offset_(0),
       max_queued_frames_(kMaxInputQueueUs * input_samples_per_second /
                          base::Time::kMicrosecondsPerSecond),
       fade_frames_remaining_(0),
       fade_out_frames_total_(0),
       zeroed_frames_(0),
+      being_skipped_(false),
       weak_factory_(this) {
   LOG(INFO) << "Create " << this;
   DCHECK(delegate_);
   DCHECK(mixer_);
   weak_this_ = weak_factory_.GetWeakPtr();
 }
 
 StreamMixerAlsaInputImpl::~StreamMixerAlsaInputImpl() {
   LOG(INFO) << "Destroy " << this;
   DCHECK(mixer_task_runner_->BelongsToCurrentThread());
@@ skipping 134 matching lines @@
     LOG(INFO) << "End of stream for " << this;
     state_ = kStateGotEos;
   } else if (state_ == kStateUninitialized) {
     state_ = kStateNormalPlayback;
   }
   mixer_->OnFramesQueued();
 }
 
 void StreamMixerAlsaInputImpl::OnSkipped() {
   DCHECK(mixer_task_runner_->BelongsToCurrentThread());
+  if (!being_skipped_) {

[slan, 2016/12/07 00:22:27]

Suggestion: I think that an integer |consecutive_frames_skipped_| would be a
little bit more readable here.

[kmackay, 2016/12/07 22:59:58]

Changed name to is_underflowing_

+    LOG(WARNING) << "Underflow for " << this;
+    being_skipped_ = true;
+  }
   if (state_ == kStateNormalPlayback) {
     // Fade in once this input starts providing data again.
     fade_frames_remaining_ = NormalFadeFrames();
   }
 }
 
 void StreamMixerAlsaInputImpl::AfterWriteFrames(
     const MediaPipelineBackendAlsa::RenderingDelay& mixer_rendering_delay) {
   DCHECK(mixer_task_runner_->BelongsToCurrentThread());
   double resampler_queued_frames =
@@ skipping 59 matching lines @@
     return std::min(available_frames, fade_frames_remaining_);
   return std::max(0, available_frames - NormalFadeFrames());
 }
 
 void StreamMixerAlsaInputImpl::GetResampledData(::media::AudioBus* dest,
                                                 int frames) {
   DCHECK(mixer_task_runner_->BelongsToCurrentThread());
   DCHECK(dest);
   DCHECK_EQ(kNumOutputChannels, dest->channels());
   DCHECK_GE(dest->frames(), frames);
+  being_skipped_ = false;
 
   if (state_ == kStatePaused || state_ == kStateDeleted) {
     dest->ZeroFramesPartial(0, frames);
     return;
   }
 
   if (resampler_) {
     resampler_->Resample(frames, dest);
   } else {
     FillFrames(0, dest, frames);
@@ skipping 187 matching lines @@
 
 void StreamMixerAlsaInputImpl::VolumeScaleAccumulate(bool repeat_transition,
                                                      const float* src,
                                                      int frames,
                                                      float* dest) {
   slew_volume_.ProcessFMAC(repeat_transition, src, frames, dest);
 }
 
 }  // namespace media
 }  // namespace chromecast